The current source is able to provide a current maintaining at a specific value (specifically, including cases that an amplitude value of an output current is a unique rated value and an amplitude value of an output current is adjustable within a certain range); thus, the current source has a wide range of applications. However, a direct current output by the current source has ripple due to an internal circuit of the current source, i.e., the direct current output by the current source includes an alternating component.
Specifically, an LED driver is a typical current source. The LED driver includes an LED driver capable of providing an LED Light with a direct current having a constant amplitude value, and an LED driver capable of providing an LED light with a direct current whose amplitude value is adjustable within a certain range, i.e., an LED driver having a dimming function.
However, in a case that the speed of a current controlling loop is low, or the capacity of a filter is small, the output current of the LED driver includes not only direct component but also alternating component, that is, current ripple occurs. In a case that the current having ripple flows through the LED light, the brightness of the LED light may change with the ripple of current, i.e., stroboscopic phenomenon occurs.
The stroboscopic phenomenon may influence the service life of the LED light, and accordingly, how to reduce the ripple of the current output by the current source becomes an urgent problem to be solved.
In addition, different current sources output currents having different amplitude values, and amounts of ripples in the currents may be different; meanwhile, for a current source whose current amplitude is adjustable, different amplitudes may result in different amounts of ripples. Thus, it is particularly important to reduce the ripples of the currents output by different current sources or by one current source whose current amplitude is adjustable.